[lexer] Pass Builders around by reference instead of implicitly Copying

lexer/src/states/begin.rs

@@ -35,7 +35,7 @@ impl State for Begin {
             StateResult::advance(Box::new(IdSub{}))
         } else if c.is_hash() {
             StateResult::advance(Box::new(Hash::new()))
-        } else if let Some(st) = Digit::with_char(Builder::new(), c) {
+        } else if let Some(st) = Digit::with_char(&Builder::new(), c) {
             StateResult::advance(Box::new(st))
         } else {
             StateResult::fail(Error::invalid_char(c))

lexer/src/states/hash.rs

@@ -28,7 +28,7 @@ impl State for Hash {
                 StateResult::advance(Box::new(Bool::new(buf.as_str())))
             },
             c if c.is_radix() || c.is_exactness() => {
-                if let Some(st) = Prefix::with_char(Builder::new(), c) {
+                if let Some(st) = Prefix::with_char(&Builder::new(), c) {
                     StateResult::advance(Box::new(st))
                 } else {
                     StateResult::fail(Error::new(format!("invalid numeric prefix character: {}", c)))

lexer/src/states/number/digit.rs

@@ -15,7 +15,7 @@ impl Digit {
         Digit(b)
     }
 
-    pub fn with_char(b: Builder, c: char) -> Option<Digit> {
+    pub fn with_char(b: &Builder, c: char) -> Option<Digit> {
         let mut b = b.clone();
         if !b.seen_radix() {
             b.push_radix(Radix::Dec);

lexer/src/states/number/mod.rs

@@ -20,7 +20,7 @@ pub enum Sign { Neg = -1, Pos = 1 }
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub enum Exact { Yes, No }
 
-#[derive(Copy, Clone, Debug)]
+#[derive(Clone, Debug)]
 pub struct Builder {
     radix: Option<Radix>,
     sign: Option<Sign>,

lexer/src/states/number/prefix.rs

@@ -18,7 +18,7 @@ impl Prefix {
         Prefix(b)
     }
 
-    pub fn with_char(b: Builder, c: char) -> Option<Prefix> {
+    pub fn with_char(b: &Builder, c: char) -> Option<Prefix> {
         if let Some(ex) = Exact::from(c) {
             if b.seen_exact() {
                 return None;
@@ -42,10 +42,10 @@ impl Prefix {
 impl State for Prefix {
     fn lex(&mut self, c: char) -> StateResult {
         if c.is_hash() {
-            StateResult::advance(Box::new(Hash(self.0)))
+            StateResult::advance(Box::new(Hash::new(&self.0)))
-        } else if let Some(st) = Sign::with_char(self.0, c) {
+        } else if let Some(st) = Sign::with_char(&self.0, c) {
             StateResult::advance(Box::new(st))
-        } else if let Some(st) = Digit::with_char(self.0, c) {
+        } else if let Some(st) = Digit::with_char(&self.0, c) {
             StateResult::advance(Box::new(st))
         } else {
             StateResult::fail(Error::invalid_char(c))
@@ -57,9 +57,15 @@ impl State for Prefix {
     }
 }
 
+impl Hash {
+    fn new(b: &Builder) -> Hash {
+        Hash(b.clone())
+    }
+}
+
 impl State for Hash {
     fn lex(&mut self, c: char) -> StateResult {
-        if let Some(st) = Prefix::with_char(self.0, c) {
+        if let Some(st) = Prefix::with_char(&self.0, c) {
             StateResult::advance(Box::new(st))
         } else {
             StateResult::fail(Error::invalid_char(c))

lexer/src/states/number/sign.rs

@@ -15,7 +15,7 @@ impl Sign {
         Sign(b)
     }
 
-    pub fn with_char(b: Builder, c: char) -> Option<Sign> {
+    pub fn with_char(b: &Builder, c: char) -> Option<Sign> {
         if !b.seen_sign() {
             match c {
                 '+' => {